Refrigerator with enhanced efficiency

ABSTRACT

The present invention relates to a refrigerator with a refrigerant circuit comprising a compressor, a condenser, an expansion device, a first evaporator downstream the expansion device, a second evaporator downstream the first evaporator, a heat exchanger to cause heat exchange between refrigerant downstream the condenser and upstream said first evaporator, on one side, and refrigerant downstream the second evaporator and upstream the compressor, on the other side.

CROSS-REFERENCE TO RELATED APPLICATIONS

This present application claims the benefit of European Patent Application No. 15161544.0 entitled “REFRIGERATOR WITH ENHANCED EFFICIENCY” filed on Mar. 27, 2015, the entire contents of which are incorporated by reference.

TECHNICAL FIELD

The present invention relates to a refrigeration device and more particularly relates to a refrigerator with enhanced efficiency.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a refrigerator with a refrigerant circuit comprising a compressor, a condenser, an expansion device, a first evaporator downstream the expansion device, a second evaporator downstream the first evaporator, a heat exchanger to cause heat exchange between refrigerant downstream the condenser and upstream said first evaporator, on one side, and refrigerant downstream the second evaporator and upstream the compressor, on the other side.

These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings, certain embodiment(s) which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. Drawings are not necessary to scale. Certain features of the invention may be exaggerated in scale or shown in schematic form in the interest of clarity and conciseness.

Further advantages and features of a refrigerator according to the present invention will be clear from the following detailed description, provided by way of non-limiting example, with reference to the attached drawings in which:

FIG. 1 is a schematic view of a refrigerant circuit of a refrigerator according to the prior art;

FIG. 2 is a schematic view of a refrigerant circuit of a refrigerator according to the present invention;

FIG. 3 is a detail of one of the two heat-exchangers of FIG. 1 according to a first embodiment, and

FIG. 4 is a detail similar to FIG. 3 and referring to a second embodiment of the invention.

DETAILED DESCRIPTION

Before the subject invention is described further, it is to be understood that the invention is not limited to the particular embodiments of the invention described below, as variations of the particular embodiments may be made and still fall within the scope of the appended claims. It is also to be understood that the terminology employed is for the purpose of describing particular embodiments, and is not intended to be limiting. Instead, the scope of the present invention will be established by the appended claims.

Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range, and any other stated or intervening value in that stated range, is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and are also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the invention.

In this specification and the appended claims, the singular forms “a,” “an” and “the” include plural reference unless the context clearly dictates otherwise.

While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the concepts of the present disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

The present invention relates to a refrigerator with a refrigerant circuit comprising a compressor, a condenser, an expansion device, a first evaporator downstream the expansion device, a second evaporator downstream the first evaporator, a heat exchanger to cause heat exchange between refrigerant downstream the condenser and upstream said first evaporator, on one side, and refrigerant downstream the second evaporator and upstream the compressor, on the other side. The refrigeration circuit of a refrigerator of the above type is shown in FIG. 1.

GB 2143014 suggests using two evaporators in the refrigeration circuit and with heat exchangers between the compressor and one of the evaporators and between the two evaporators respectively. This known solution is quite complex since it uses a diverter valve, two capillary tubes and a suction pipe from the compressor which has a fork, one arm leading to one evaporator and the other arm leading to the other evaporator.

It is therefore an object of the present invention to provide a refrigerator with a refrigerant circuit of the kind mentioned at the beginning of the description, which has enhanced energy efficiency and it is simple and easy to be manufactured. Such object is reached tanks to the features listed in the appended claims. The refrigeration circuit of a refrigerator according to the invention presents an additional heat exchanger to cause heat exchange between refrigerant downstream the condenser and upstream the first evaporator, on a first side, and refrigerant downstream the first evaporator and upstream the second evaporator, on a second side, the expansion device being a single capillary tube that is configured to act as said first side of both heat exchangers.

By adding a further heat exchanger to the refrigeration circuit of a known refrigerator the title of vapor of refrigerant at the evaporator inlet is reduced. Therefore refrigerant has more liquid that can evaporate in the evaporator, increasing the efficiency of the system. The solution according to the invention gives benefit in terms of low energy consumption if compared to known more expensive solutions, for instance use of vacuum insulated panels or variable speed compressors. Of course, the solution according to the invention may be used also in combination with these known measures in order to further increase the efficiency of the refrigerator.

A type of refrigerator similar to the one according to the present invention is known from “dual evaporator” or “sequential evaporator” type refrigerators, but these refrigerators use a non-azeotropic mixture of at least two different refrigerants, for instance propane (R-290) and n-butane (R-600), which has an appropriate gliding temperature difference (GTD) during evaporation and condensation phases. With a refrigeration cycle using the above mixture, known also as Lorenz-Meutzner cycle, it is possible to have identical or at least similar energy saving performances of a dual evaporator refrigeration circuit using a mono-component refrigerant and a by-pass two-circuit cycle, where a 3-way electrovalve is used.

A refrigerator of this type is disclosed by U.S. Pat. No. 5,207,077 and EP 2592366. In both the above documents the expansion device is placed immediately upstream the first evaporator, i.e. the low-temperature evaporator. In U.S. Pat. No. 5,207,077 the expansion device is identified in the drawing as an expansion valve, while in EP 2592366 the expansion device is a capillary tube arranged at the side of the first evaporator. In said first solution the presence of the valve does increase the overall cost of the appliance, and it may create problem of condensation on suction tube. In the second solution, as it is also disclosed in “Performance optimization of a Lorenz-Meutzner cycle charged with hydrocarbon mixtures for a domestic refrigerator-freezer”, IJR, N. 35, Issue 1, January 2012, pages 36-46, the optimum capillary tube length is of the order of 10-15 m if similar energy consumption performances of a bypass two-circuit cycle are to be obtained.

In the above documents the sub-cooling from second evaporator and compressor and the additional one required by using these mixtures (tube connection between first and second evaporator) is obtained through use of heat exchangers made with two tubes. In EP 2592366 it is explained that these tubes work better in case one is inside the other and in counter-flow.

On the above mentioned publication and patents indications are given also on modifications required by a refrigerator/freezer product using a non-azeotropic mixture. In the above mentioned article “Performance optimization of a Lorenz-Meutzner cycle charged with hydrocarbon mixtures for a domestic refrigerator-freezer” are given also information on modification in length of capillary (required at least 10 m) in order to have benefits in energy and correct behavior of product.

The applicant has also made experimental work on a refrigeration circuit designed for a modified Lorenz-Meutzner cycle which does not present the above problems and has a low cost. According to such modification the expansion device is a capillary tube that is configured to act as said first side of both heat exchangers.

According to the solution developed by the applicant for a non-azeotropic mixture, the capillary tube is used externally to the other tubes of the refrigerant circuit, and the refrigerant flow in the capillary tube is in counter flow with reference to the refrigerant flow in the tube of the refrigerant circuit. Of course the capillary tube may be used internally to the other tube.

Even if the above results are promising, the solution tested by the applicant may require a loading of the refrigerant circuit with a mixture of refrigerants having a certain composition and distribution. Accordingly, the loading may implicate an increased cost and an increased complexity in the manufacturing process of the refrigerator.

According to the invention, the applicant has surprisingly discovered that the same circuit designed for a non-azeotropic mixture of refrigerants presents thermodynamic advantages even if used with a single refrigerant, i.e. a refrigerant whose composition is made mainly by a single chemical compound. This result could not be expected and therefore the choice of using a circuit specifically designed for a non-azeotropic mixture of refrigerants for a single mono-compound refrigerant could not be predicted by a person skilled in the art.

According to a preferred feature of the invention, for a first heat exchanger (the one obtained with capillary tube and suction tube connecting the freezer evaporator to the fridge evaporator) the single capillary tube is parallel and in contact with the tube from the freezer evaporator, and has a length of at least 700 mm.

According to a second embodiment of the invention, for the first heat exchanger the capillary tube is wrapped around the tube from the freezer evaporator, and has a length of at least 1000 mm, with a contact length on such tube of at least 400 mm.

The second heat exchanger between the capillary tube and the suction tube upstream the compressor is dimensioned as in traditional refrigerators. With reference to the drawings, and particularly to FIGS. 2-4, the refrigerant circuit according to the invention comprises a compressor 10 and a condenser 12. The condenser 12 may be placed on a back wall of the refrigerator and cooled by natural convection or with forced air. The refrigerant circuit further comprises a drier 14 as normally used on a domestic refrigerator/freezer appliance. Downstream the drier 14, the circuit comprises a single capillary tube 16 with an internal diameter comprised between 0.60 and 0.80 mm. In FIG. 1, the capillary tube 16 is schematically represented as a tube with a plurality of loops, only for distinguishing it from the suction tube (in the technical field of domestic refrigerators it is usual to represent a capillary in this way).

The refrigerant circuit comprises a first heat exchanger 18 and a second heat exchanger 20. The first heat exchanger 18 presents a first side made by a capillary tube portion 16 a in contact with a portion of the circuit tube between first or low temperature evaporator 17 (placed in the freezer compartment—not shown) and second or higher temperature evaporator 19 (placed in the fridge compartment—not shown). A detailed view of the heat exchanger 18 is shown in FIG. 3. Applicant has determined through experimental tests that the length of this tube/tube heat exchanger (with two parallel straight tubes taped together by means of an adhesive aluminum tape—not shown in the drawings for sake of clarity) is preferably at least 0.7 m. In some embodiments, the length of the tube/tube heat exchanger may be more than 1 m. The total length of the capillary tube 16 a is preferably higher than 3.5 m. An internal diameter of the suction tube 22 is preferably comprised between 5 and 8 mm.

According to a further embodiment shown in FIG. 4, the capillary tube 16 a is wrapped around the tube 22 of the refrigerant circuit with use of an aluminum tape (not shown). The length of the suction tube 22, on which the capillary tube 16 a is spirally wound, is preferably higher than 0.4 m. The capillary tube 16 a may have a corresponding length greater than 1 m.

Referring again to FIGS. 2-4, the second heat exchanger 20 is similarly composed of a capillary tube portion 16 b and a portion 24 of a suction tube upstream of the compressor 10. The length of the double-pipe heat exchanger 20 is substantially similar to that utilized in conventional refrigerators, and therefore it will not be further described here. The solution according to the invention can be applied to direct cooled evaporator products (static evaporators in freezer and fridge compartments) and hybrid products (no frost freezer and static fridge).

Testing activity carried out by the applicant in a refrigerator (with freezer and fridge compartments) having a total internal volume around 300 liters, shows the main benefits obtained applying the cycle according to the invention on a bottom mount freezer built-in product and by using a single refrigerant. Such advantages are still significant if a comparison is made between the technical solution according to the invention and a sample previously tested with a non-azeotropic mixture of hydrocarbons refrigerants, for instance propane/normal butane (R290/R600).

A refrigerator/freezer direct cooled with evaporators in series has been tested (according to Standard IEC 62552) and results are as follows:

-   -   With mixture R290/R600a (20/80): energy consumption 424 Wh/24 h     -   With single refrigerant R600a: energy consumption 447 Wh/24 h         (+4.9%)         Energy consumption of the same product without the additional         heat exchanger according to the invention has an energy         consumption of approximately 470 Wh/24 h, therefore about 5%         higher if compared to a refrigerator according to the invention.

The testing of the novel refrigerator discussed herein demonstrate that the additional heat exchanger cools down more refrigerant in the capillary. The cooling of the refrigerant provides for the refrigerant to enter the evaporator with less vapor. The refrigerant entering with less vapor has been shown to increase the evaporator efficiency. In the tests carried out by the applicant, a capillary mass flow rate of 4.1 l/min (measured with nitrogen at 10 bar) was used. However, the disclosed solution can be applied with different flow rates (e.g. flow rates from 3.8 l/min to 5 l/min). 

The invention claimed is:
 1. A refrigerator with a refrigerant circuit comprising: a compressor; a condenser; an expansion device corresponding to a capillary tube; a first evaporator downstream the expansion device; a second evaporator downstream the first evaporator; a first heat exchanger configured to cause heat exchange between refrigerant downstream the condenser and upstream the first evaporator, on a first side, and refrigerant downstream the second evaporator and upstream the compressor, on a second side; and a second heat exchanger configured to cause heat exchange between refrigerant downstream the condenser and upstream the first evaporator, on the first side, and refrigerant downstream the first evaporator and upstream the second evaporator, on the second side, wherein the expansion device is configured to act as the first side of the first heat exchanger and the second heat exchanger.
 2. The refrigerator according to claim 1, wherein the refrigerant comprises a single compound.
 3. The refrigerator according to claim 1, wherein the first heat exchanger and the second heat exchanger are shaped as double-pipe exchangers formed by the capillary tube in a heat exchange relationship with the second side corresponding to a return line of the refrigerant circuit.
 4. The refrigerator according to claim 3, wherein the capillary tube is externally in contact the return line.
 5. The refrigerator according to claim 1, wherein the capillary tube has a total length greater than 3.5 m.
 6. The refrigerator according to claim 5, wherein the length of the second heat exchanger is greater than 0.7 m.
 7. The refrigerator according to claim 1, wherein the first heat exchanger and the second heat exchanger are formed by the capillary tube and by a return line in parallel one against the other.
 8. The refrigerator according to claim 1, wherein at least one of the first heat exchanger and the second heat exchanger is made by a return line defining the second side of the heat exchangers and by a the capillary tube wrapped around the return line.
 9. The refrigerator according to claim 1, wherein at least one of the first heat exchanger and the second heat exchanger is covered by an aluminum layer.
 10. The refrigerator according to claim 1, wherein the first evaporator and the second evaporator are static evaporators disposed in a freezer compartment and in a fridge compartment respectively.
 11. The refrigerator according to claim 1, wherein the second evaporator is a static evaporator disposed in a fridge compartment, and the first evaporator is a no-frost evaporator disposed in a freezer compartment.
 12. The refrigerator according to claim 1, wherein the refrigerant is n-butane.
 13. A refrigeration system comprising: a compressor; a condenser; an expansion device; a first evaporator downstream the expansion device; a second evaporator downstream the first evaporator; a first heat exchanger; a second heat exchanger, wherein the system forms a refrigerant circuit comprising: the first heat exchanger positioned upstream the second heat exchanger along the expansion device defining a first side and positioned downstream the second evaporator along a return line defining a second side; and the second heat exchanger positioned upstream the first evaporator along the expansion device on the first side and positioned downstream the first evaporator along the return line on the second side.
 14. The system according to claim 13, wherein the at least a portion of the return line corresponds to a suction line.
 15. The system according to claim 13, wherein the expansion device corresponds to a capillary tube.
 16. The system according to claim 14, wherein the capillary tube is externally in contact with the return line.
 17. The system according to claim 14, wherein the capillary tube has a total length greater than 3.5 m.
 18. The system according to claim 17, wherein the length of the second heat exchanger is greater than 0.7 m.
 19. The system according to claim 14, wherein the first heat exchanger and the second heat exchanger are formed by the expansion device and by the return line in parallel one against the other.
 20. The system according to claim 14, wherein at least one of the first heat exchanger and the second heat exchanger is formed by a return line defining the second side of the at least one heat exchanger and by a the expansion device wrapped around the return line. 